IEqualityComparer for Annoymous Type

首先，我看到了匿名类型的IEqualityComparer，那里的答案没有回答我的问题，原因很明显，我需要IEqualityComparer而不是IComparer来与Linq的Distinct()方法一起使用。我也检查了其他答案，但这些都不是解决方案。。。

问题

我有一些代码可以操作并从DataTable 中提取记录

var glext = m_dtGLExt.AsEnumerable();
var cflist =
    (from c in glext
     orderby c.Field<string>(m_strpcCCType), 
             c.Field<string>(m_strpcCC), 
             c.Field<string>(m_strpcCCDesc),
             c.Field<string>(m_strpcCostItem)
     select new
     {
        CCType = c.Field<string>(m_strpcCCType),
        CC = c.Field<string>(m_strpcCC),
        CCDesc = c.Field<string>(m_strpcCCDesc),
        CostItem = c.Field<string>(m_strpcCostItem)
     }).Distinct();

但我需要这种不同的方法不区分大小写。让我陷入困境的是匿名类型的使用。

尝试的解决方案1

如果我有SomeClass，它有具体的物体，我显然可以做

public class SumObject
{
    public string CCType { get; set; }
    public string CC { get; set; }
    public string CCDesc { get; set; }
    public string CostItem { get; set; }
}

我显然可以做这个

List<SumObject> lso = new List<SumObject>() 
{
    new SumObject() { CCType = "1-OCC", CC = "300401", CCDesc = "Rooney", CostItem = "I477" },
    new SumObject() { CCType = "1-OCC", CC = "300401", CCDesc = "Zidane", CostItem = "I677" },
    new SumObject() { CCType = "1-OCC", CC = "300401", CCDesc = "Falcao", CostItem = "I470" },
};
var e = lso.Distinct(new SumObjectComparer()); // Great :]

其中

class SumObjectComparer : IEqualityComparer<SumObject>
{
    public bool Equals(SumObject x, SumObject y)
    {
        if (Object.ReferenceEquals(x, y)) 
            return true;
        if (Object.ReferenceEquals(x, null) || Object.ReferenceEquals(y, null))
            return false;
        return x.CCType.CompareNoCase(y.CCType) == 0 && 
               x.CC.CompareNoCase(y.CC) == 0 && 
               x.CCDesc.CompareNoCase(y.CCDesc) == 0 && 
               x.CostItem.CompareNoCase(y.CostItem) == 0;
    }
    public int GetHashCode(SumObject o)
    {
        if (Object.ReferenceEquals(o, null)) 
            return 0;
        int hashCCType = String.IsNullOrEmpty(o.CCType) ? 
            0 : o.CCType.ToLower().GetHashCode();
        int hashCC = String.IsNullOrEmpty(o.CC) ? 
            0 : o.CC.ToLower().GetHashCode();
        int hashCCDesc = String.IsNullOrEmpty(o.CCDesc) ? 
            0 : o.CCDesc.ToLower().GetHashCode();
        int hashCostItem = String.IsNullOrEmpty(o.CostItem) ? 
            0 : o.CostItem.ToLower().GetHashCode();
        return hashCCType ^ hashCC ^ hashCCDesc ^ hashCostItem;
    }
}

然而，在上面的Linq查询中使用匿名类型让我大吃一惊

尝试的解决方案2

为了尝试另一种解决方案（因为我在其他地方也有同样的问题），我生成了以下通用比较器类

public class GenericEqualityComparer<T> : IEqualityComparer<T>
{
    Func<T, T, bool> compareFunction;
    Func<T, int> hashFunction;
    public GenericEqualityComparer(Func<T, T, bool> compareFunction, Func<T, int> hashFunction)
    {
        this.compareFunction = compareFunction;
        this.hashFunction = hashFunction;
    }
    public bool Equals(T x, T y) { return compareFunction(x, y); }
    public int GetHashCode(T obj) { return hashFunction(obj); }
}

这样我就可以尝试做

var comparer = new GenericEqualityComparer<dynamic>(
    (x, y) => { /* My equality stuff */ }, 
    o => { /* My hash stuff */ });

但这将返回的值强制转换为IEnumerable<dynamic>，这反过来又影响了我即将使用的cflist，因此在接下来的查询中join失败。

 var cf = 
    (from o in cflist
     join od in glext
     on new { o.CCType, o.CC, o.CCDesc, o.CostItem } equals new
     {
        CCType = od.Field<string>(m_strpcCCType),
        CC = od.Field<string>(m_strpcCC),
        CCDesc = od.Field<string>(m_strpcCCDesc),
        CostItem = od.Field<string>(m_strpcCostItem)
     }
     into c
     select new { ... }

由于大量使用此代码，我不想在IEnumerable<T>之间进行难看的转换。。。

问题

有没有一种方法可以为我的匿名类型创建IEquailityComparer？

谢谢你抽出时间。

public static class InferredEqualityComparer
{
    public static IEqualityComparer<T> Create<T>(
        IEnumerable<T> example,
        Func<T, T, bool> equalityCheck,
        Func<T, int> hashCodeProvider)
    {
        return new EqualityComparerImpl<T>(equalityCheck, hashCodeProvider);
    }
    private sealed class EqualityComparerImpl<T> : IEqualityComparer<T>
    {
        // Implement in the obvious way, remembering the delegates and
        // calling them appropriately.
    }
}

var glext = m_dtGLExt.AsEnumerable();
var query = from c in glext
            orderby ...
            select new { ... };
var comparer = InferredEqualityComparer.Create(query,
    (x, y) => { ... },
    o => { ... }
);
var distinct = query.Distinct(comparer);

var sample = new[] { new { ... } };
var comparer = InferredExqualityComparer.Create(sample, ...);
var distinct = (... query here ... ).Distinct(comparer);